1. Technical Field
The present invention relates to display sheets, display devices, electronic apparatuses, and methods for producing display sheets.
2. Related Art
Electrophoretic displays utilizing the electrophoresis of particles are known as components that have been employed for the image display section of electronic paper (see, for example, Japanese Patent No. 4348180). The electrophoretic displays have excellent portability and low power consumption, and are particularly suited as the image display section of electronic paper.
Japanese Patent No. 4348180 discloses a display having a front plane that includes a light-transmissive substrate, a light-transmissive electrode, an electro-optic layer and a lamination adhesive layer stacked in this order, and a backplane that is stacked on the lamination adhesive layer. The electro-optic layer has microcapsules each containing white and black electrophoretic particles. Such displays show white color by arranging the white electrophoretic particles on the light-transmissive substrate side in each microcapsule. When light is incident on the electro-optic layer (the microcapsules) through the light-transmissive substrate and the light-transmissive electrode, the white electrophoretic particles in the microcapsules reflect and diffuse the light through the light-transmissive substrate and the light-transmissive electrode.
As this mechanism shows, white color display involves incident light passing through the light-transmissive substrate and the light-transmissive electrode two times. According to the above patent, the light-transmissive substrate and the light-transmissive electrode are both colorless and transparent. However, the light transmittance through the stacked layers is not 100% but is usually 80% to 90%. Provided that the substrate has a light transmittance of 80%, the light coming out through the light-transmissive substrate and the light-transmissive electrode has only 64% of the intensity of the incident light as a result of having passed the substrate two times (80%×80%). Accordingly, the displays of Japanese Patent No. 4348180 cannot achieve a high reflectance of white light and are thus incapable of displaying luminous images.
A possible approach to solve such problems, namely to increase the light transmittance of the substrate, is to reduce the thickness of the light-transmissive electrodes. However, reducing the thickness of the light-transmissive electrodes correspondingly increases the electrical resistance of the light-transmissive electrodes. Consequently, voltage drops (uneven voltages within a plane of a light-transmissive electrode) occur when a voltage is applied to the light-transmissive electrodes, and an electric field cannot be applied with the desired intensity to the microcapsules. As a result, the displays cannot be operated stably, and display properties are deteriorated.
As described above, there is a trade-off between increasing the white color reflectance and maintaining display properties with the displays of Japanese Patent No. 4348180.